A study of the prevalence and severity of diabetic retinopathy will be conducted in a group of 2,400 diabetic patients in their home communities. Objective recording of retinopathy by use of stereoscopic fundus photography combined with a standardized protocol for grading the retinopathy will be used. Grading of the stereo photographs will provide a sensitive and reproducible method for detection of retinopathy. The frequency and causes of visual impairment will be determined. The prevalence of retinopathy and of its various component lesions will be evaluated with respect to duration and age at diagnosis of diabetes, blood pressure level and smoking history.